netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 108 insertions, 0 deletions

diff --git a/drivers/usb/chipidea/ulpi.c b/drivers/usb/chipidea/ulpi.c
new file mode 100644
index 000000000..dfec07e8a
--- /dev/null
+++ b/drivers/usb/chipidea/ulpi.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2016 Linaro Ltd.
+ */
+
+#include <linux/device.h>
+#include <linux/usb/chipidea.h>
+#include <linux/ulpi/interface.h>
+
+#include "ci.h"
+
+#define ULPI_WAKEUP		BIT(31)
+#define ULPI_RUN		BIT(30)
+#define ULPI_WRITE		BIT(29)
+#define ULPI_SYNC_STATE		BIT(27)
+#define ULPI_ADDR(n)		((n) << 16)
+#define ULPI_DATA(n)		(n)
+
+static int ci_ulpi_wait(struct ci_hdrc *ci, u32 mask)
+{
+	unsigned long usec = 10000;
+
+	while (usec--) {
+		if (!hw_read(ci, OP_ULPI_VIEWPORT, mask))
+			return 0;
+
+		udelay(1);
+	}
+
+	return -ETIMEDOUT;
+}
+
+static int ci_ulpi_read(struct device *dev, u8 addr)
+{
+	struct ci_hdrc *ci = dev_get_drvdata(dev);
+	int ret;
+
+	hw_write(ci, OP_ULPI_VIEWPORT, 0xffffffff, ULPI_WRITE | ULPI_WAKEUP);
+	ret = ci_ulpi_wait(ci, ULPI_WAKEUP);
+	if (ret)
+		return ret;
+
+	hw_write(ci, OP_ULPI_VIEWPORT, 0xffffffff, ULPI_RUN | ULPI_ADDR(addr));
+	ret = ci_ulpi_wait(ci, ULPI_RUN);
+	if (ret)
+		return ret;
+
+	return hw_read(ci, OP_ULPI_VIEWPORT, GENMASK(15, 8)) >> 8;
+}
+
+static int ci_ulpi_write(struct device *dev, u8 addr, u8 val)
+{
+	struct ci_hdrc *ci = dev_get_drvdata(dev);
+	int ret;
+
+	hw_write(ci, OP_ULPI_VIEWPORT, 0xffffffff, ULPI_WRITE | ULPI_WAKEUP);
+	ret = ci_ulpi_wait(ci, ULPI_WAKEUP);
+	if (ret)
+		return ret;
+
+	hw_write(ci, OP_ULPI_VIEWPORT, 0xffffffff,
+		 ULPI_RUN | ULPI_WRITE | ULPI_ADDR(addr) | val);
+	return ci_ulpi_wait(ci, ULPI_RUN);
+}
+
+int ci_ulpi_init(struct ci_hdrc *ci)
+{
+	if (ci->platdata->phy_mode != USBPHY_INTERFACE_MODE_ULPI)
+		return 0;
+
+	/*
+	 * Set PORTSC correctly so we can read/write ULPI registers for
+	 * identification purposes
+	 */
+	hw_phymode_configure(ci);
+
+	ci->ulpi_ops.read = ci_ulpi_read;
+	ci->ulpi_ops.write = ci_ulpi_write;
+	ci->ulpi = ulpi_register_interface(ci->dev, &ci->ulpi_ops);
+	if (IS_ERR(ci->ulpi))
+		dev_err(ci->dev, "failed to register ULPI interface");
+
+	return PTR_ERR_OR_ZERO(ci->ulpi);
+}
+
+void ci_ulpi_exit(struct ci_hdrc *ci)
+{
+	if (ci->ulpi) {
+		ulpi_unregister_interface(ci->ulpi);
+		ci->ulpi = NULL;
+	}
+}
+
+int ci_ulpi_resume(struct ci_hdrc *ci)
+{
+	int cnt = 100000;
+
+	if (ci->platdata->phy_mode != USBPHY_INTERFACE_MODE_ULPI)
+		return 0;
+
+	while (cnt-- > 0) {
+		if (hw_read(ci, OP_ULPI_VIEWPORT, ULPI_SYNC_STATE))
+			return 0;
+		udelay(1);
+	}
+
+	return -ETIMEDOUT;
+}